Add my own wall into archipack addon
It mostly depends on the kind of variations you want to achieve. 

If it is related to wall general shape, such as L T predefined parts, you may use "custom objects" (mesh based closed volumes) as walls, this is a feature of 1.3.8+ 1.4_dev free versions for blender 2.79, available on github repository.  https://github.com/s-leger/archipack/archive/140_dev.zip

In archipack 2.0 Pro version for blender 2.8, presets parameters exclude any "segments" one, as they are meant to quickly change wall's aspect (width / height / finishings, materials..) without changing the general shape.

Adding new kind of parametric objects to archipack is not an easy task as the archipack's framework require some time to getting started.